What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) During an instructional flight, the instructor noticed a loss of power in manuevering flight with the power initially set at 21' mp at 2200 RPM. An increase in oil temperature was noted although the oil pressure remained constant and within normal ranges. The a/c was turned back to the Eugene, Oregon airport when a severe vibration was experienced and the engine was shut down to prevent structural damage. An emergency landing was performed to the ground in a nearby hay field. There was no damage to the a/c, and no injuries occurred. FAA maintenance personnel inspected the engine and found bearing material throughout the oil system. Further investigation revealed rear main bearing failure leading to crankshaft fatigue separation at the number 4 crankshaft pin.
As the FAA filed it
(-23) DURING AN INSTRUCTIONAL FLIGHT, THE INSTRUCTOR NOTICED A LOSS OF POWER IN MANUEVERING FLIGHT WITH THE POWER INITIALLY SET AT 21' MP AT 2200 RPM. AN INCREASE IN OIL TEMPERATURE WAS NOTED ALTHOUGH THE OIL PRESSURE REMAINED CONSTANT AND WITHIN NORMAL RANGES. THE A/C WAS TURNED BACK TO THE EUGENE, OREGON AIRPORT WHEN A SEVERE VIBRATION WAS EXPERIENCED AND THE ENGINE WAS SHUT DOWN TO PREVENT STRUCTURAL DAMAGE. AN EMERGENCY LANDING WAS PERFORMED TO THE GROUND IN A NEARBY HAY FIELD. THERE WAS NO DAMAGE TO THE A/C, AND NO INJURIES OCCURRED. FAA MAINTENANCE PERSONNEL INSPECTED THE ENGINE AND FOUND BEARING MATERIAL THROUGHOUT THE OIL SYSTEM. FURTHER INVESTIGATION REVEALED REAR MAIN BEARING FAILURE LEADING TO CRANKSHAFT FATIGUE SEPARATION AT THE NUMBER 4 CRANKSHAFT PIN.